I agree on the range of options. I rarely used 3 or 4 on the old blocks. I'm not going over 4 on the new ones. I'd happily trade a couple of the higher end options for some smaller ports. At one point I asked Alex about getting some undrilled valves for the old type 1. That didn't happen.

I think some of the issue is blow by. Not sure how much tighter you could make the block/valve fit and not have it be a problem for maintenance/adjustability.

With the gas block being attached via a set screw, blow by is a significant issue. Frankly, these rifles shouldn't run as well as they do considering the relatively loose fit up of the gas block to the bbl boss. That's actually one of the more impressive feats of the XCR, IMO.

"Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

Question for you: Are the bbl bosses all in the same position in relation to the Type 1 vs. Type 3 gas blocks? In other words, can you swap a Type 3 gas block on to a bbl that originally came with the Type 1 block? I'm assuming so from earlier comments you've made.

The reason I ask is I've been meaning to buy a spare bbl for my mini upper....not sure if the Type 1 gas blocks are even offered anymore. That means I'll have to switch over to the Type 3 (if that's the case)...but I'm not sure my current brake will clear the nub on the front side of the Type 3 gas block as it actually touches the Type 1 (the dumbass smith I had cut the bbl was supposed to cut it to 9"...which I marked on the bbl and he somehow managed to cut down to 8 5/16" since he didn't follow normal protocol and measure from the bolt face and instead measured from the bbl extension).

I know I'll have to buy a new gas tube (pretty sure the existing piston itself is fine and will work with a Type 3 block).

"Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

I think the gas block and plug would have perfect candidates for a QPQ/nitride finish, help with cleaning and erosion from the hot gasses. This, I think, would help keep the tolerance tighter for longer and then smaller port sizes because the gas block assembly has a tighter fit internally.

The Type 3 OS has a Gas Block with an 8 position gas adjustment dial — 0 through 8. It uses the Type 1 Oprod, but uses a Type 3 Gas Tube which has holes and a wider notch on one side. The Type 3 OS was designed for use on XCR-L Upper Receivers which require the Gas Block to be contained inside the Upper Receiver. The Type 3 OS can be used on any XCR-L.

All the blocks are a direct swap. RA has said, not recently, that you can still get type 1 blocks. I'll have to measure how far the type 3 dial sticks out relative to the type 1 dial.. I've never had an issue with the set screw coming loose.

Sean, not sure if we're talking about the same thing... I was referring to blow by between the valve and the body of the block. I think you're talking about gas between the barrel and the block. Right?

All the blocks are a direct swap. RA has said, not recently, that you can still get type 1 blocks. I'll have to measure how far the type 3 dial sticks out relative to the type 1 dial.. I've never had an issue with the set screw coming loose.

Sean, not sure if we're talking about the same thing... I was referring to blow by between the valve and the body of the block. I think you're talking about gas between the barrel and the block. Right?

Sorry....yes, I was talking about the blow by between the bbl and gas block. Thanks for the info on block swap-ability (both Nate and fmunk).

"Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger